CONTRADICTING EVIDENCE: We retrospectively included metastatic NSCLC patients harboring HER2 alterations who treated with afatinib….Patients with HER2 exon 20 mutations had numerically worse ORR (17% vs 42%), shorter PFS (2.6 vs 5.8 months, HR, 2.5; 95% CI, 1.2-5.5; P = 0.015) and OS (12.9 vs 33.3 months, HR, 4.4; 95% CI, 1.3-14.8; P = 0.009) than patients with other mutations.

For the response to afatinib, ERBB2ex20ins as a subclonal variant was an independent factor relating to shorter PFS [median PFS: 1.2 m (95% CI: 0.8-1.6 m) vs. 4.3 m (95% CI: 3.3-5.3 m), p < 0.05]….Moreover, the clonality status of ERBB2ex20ins was identified as a potential indicator for response to afatinib.

...epidermal growth factor receptor (EGFR) kinase domain mutations are a common cause of non-small-cell lung cancer (NSCLC), a major subtype of lung cancers. Patients harboring most of these mutations respond well to the EGFR inhibitors Gefitinib and Erlotinib initially, but soon develop resistance to them due to the emergence of the gatekeeper mutation T790M.